<div dir="ltr"><br><br><div class="gmail_quote">On Tue, Oct 21, 2008 at 9:40 AM, Mike Perkins <span dir="ltr"><<a href="mailto:mikep@randomtraveller.org.uk">mikep@randomtraveller.org.uk</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div><div></div>[...]<br></div><br>
If you are planning on using external sensors, rather than the ones on the<br>
motherboard, where do you expect to site them? I would naturally expect them to<br>
be somewhere near the items being monitored. If so, then there will be a certain<br>
level of decoupling from the fans which you are controlling, given that most<br>
fans are in the front, back or occasionally sides of the case, and not next to<br>
the items being cooled. How do you plan to handle the feedback delay? And how do<br>
you determine that the big fan you screwed into the back of the box is,<br>
actually, contributing to the cooling of the particular component you are<br>
monitoring? Airflow is not an exact science, after all[1].<br>
<br>
These questions are not intended as criticisms, rather just to satisfy my curiosity.<br>
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--<br>
<br>
Mike Perkins<br>
</font></blockquote><div><br>You are correct - it's not an exact science and what makes matters even worse is the fact that most computer cases control air flow like a sieve.<br><br>I had planned to monitor only the exhaust air temperature. Cooling the rest is a matter of controlling how air enters the case from the outside... which means I have to figure out some way to plug a lot of holes.<br>
<br>As for individual components, the best we can do is to figure out an acceptable difference between the temperature of the component and the temperature of the ambient air that is cooling that component. I think the exhaust air would be a good indicator of just how much heat we are creating since we know that the result is room temperature + component heat contribution.<br>
<br>Yes this does ignore the temperature of the air entering the case, but we would still compensate for variances in room temperature if we are trying to regulate the exhaust air to some fixed value. Room temperature air plus some added heat from the components would yield a higher exhaust temperature if the room is warmer. Therefore, the speed of the fan would have to increase to compensate. <br>
<br>Of course, we can always add passive heat sinks where necessary to further improve heat transfer to the air, if required. <br><br>--Darrin<br></div></div><br></div>